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FXAK67 PAJK 120053 AAA
AFDAJK

Southeast Alaska Forecast Discussion...UPDATED
National Weather Service Juneau AK
453 PM AKDT Thu Jul 11 2024

.UPDATE...Update to add a hydrology section for the weekend.
Changed the statement from special weather to and HY.O product.


&&

.PREV DISCUSSION......ISSUED AT 320 pm July 11 ...

.SHORT TERM...Satellite imagery this afternoon showing the
remnants of the previous days front over British Columbia with
the next low that will reach SE AK tracking towards the NE Gulf.
Heavy rain from yesterday brought up levels on local rivers and
streams but most have already crested. For tonight rain will
increase over the northern half of the panhandle as the front
associated with the approaching low moves inland. By the early
morning the low will have weakened to an open wave trough and the
front will begin to shear apart. Rainfall rates and spread will
diminish into Friday afternoon and evening with the south seeing
the least amount of precipitation. Southerly winds drop over as
the evening progresses and pressure gradient eases. An increase in
speeds again tomorrow as the front moves inland but overall the
range will be 10 to 15 kt with Lynn Canal closer to 15 to 20 kt.

.LONG TERM.../Saturday through Wednesday/ Continuing from the
short range, the break over the panhandle will be relatively brief
as our next system moves into the northern gulf by late Saturday
morning. As mentioned in the special weather statement sent out
Wednesday evening, this system is expected to bring a strong
frontal band into the panhandle through the day Sunday and bring
widespread moderate to heavy rainfall through late Sunday night
into Monday morning, with heaviest rainfall expected along the NE
gulf coast and along the Icy Strait Corridor. The orientation and
progression of this front could strongly influence rainfall totals
during this time depending on where the plume of moisture sets
up and how much it wobbles. Ensemble model guidance continues to
support high probabilities of 24 hour precipitation totals greater
than 1 inch for the above mentioned areas. As of this forecast,
the highest rainfall totals are expected along the NE gulf coast
and Yakutat, with a 60% or greater chance of 2.5 inches or more in
a 24 hour period. The expected timing of the heaviest rain
remains Sunday morning through early Monday morning, progressing
from west to east, with peak timing sometime Sunday afternoon or
evening. Through the day Monday the front is expected to begin
shearing apart with moisture transport on a downward trend and as
such should see precipitation begin to lighten up and a potential
transition to showers as opposed to persistent rain. However cloud
cover overall is expected to persist with Wednesday still giving
the best chance for more breaks. With this expected heavy rain,
many area streams and rivers are likely to see significant rises
during this timeframe. Close coordination with the Alaska River
Forecast Center continues as flood potential is assessed as the
event approaches.

In term of winds, this strong frontal band is likely to produce
low end gales west of Yakutat due to development of a barrier jet.
For the NE gulf coast expectations are for high end small craft
winds of around 30 kt by late Saturday night into Sunday morning.
The front will then gradually push inland through Sunday afternoon
and into the evening. This will lead to increasing winds of 15 kt
or more along the front, especially for the northern and central
inner channels. For land areas along the Icy Strait corridor as
well as outer coastal communities, can expect gusts up to 30 mph
with the frontal passage, with winds across the panhandle trending
downwards Monday night into Tuesday.

Looking towards the middle of next week we are likely to have a
brief lull between systems, though the pattern overall looks to
remain active.

&&

.AVIATION...Today has been mostly MVFR to VFR conditions. This is
all ahead of the next front that is expected to move in later
this afternoon with aviation impacts lasting through the
overnight.

As the next front and round of weather tracks through, conditions
will deteriorate as rainfall increases. Aviation conditions will
drop, mainly due to CIG, to IFR to low-end MVFR. There is evidence
of LIFR conditions possible overnight with CIGs getting close to 500
feet.

&&

.HYDROLOGY...Prolonged rain event starting Saturday and continuing
into Monday. Could last 24 to 36 hours in duration. The most
favored location for heaviest amounts is Northeast Gulf coast and
northern panhandle. Converted SPS into a HY.o product.

/ From long term section / Ensemble model guidance continues to
support high probabilities of 24 hour precipitation totals greater
than 1 inch for the above mentioned areas. As of this forecast,
the highest rainfall totals are expected along the NE gulf coast
and Yakutat, with a 60% or greater chance of 2.5 inches or more in
a 24 hour period. The expected timing of the heaviest rain
remains Sunday morning through early Monday morning, progressing
from west to east, with peak timing sometime Sunday afternoon or
evening.


&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ643-644-651-652-664-671-672.

&&

$$

SHORT TERM...PRB
LONG TERM....STJ
AVIATION...GJS
HYDROLOGY...Bezenek

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